Conflict avoidance in random access channel (RACH) resources in integrated access and backhaul (IAB) networks

ABSTRACT

Certain aspects of the present disclosure provide techniques for avoiding conflicts of resources assigned to one or more signals with resources assigned to Random Access Channel (RACH) in an Integrated Access and Backhaul (IAB) network. Configurations for first and second sets of signals are obtained for a first and second base station (BS) respectively. Based on the obtained configurations, a RACH configuration is determined for the first BS for performing a RACH procedure with the second BS over a wireless backhaul link, wherein one or more Physical RACH (PRACH) occasions according to the determined RACH configuration do not conflict with resources used for at least one of the first or the second set of signals. The determined RACH configuration is communicated to the second BS, wherein the second BS transmits a RACH signal to the first BS based on the determined RACH configuration.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional application of U.S. application Ser.No. 16/409,400, filed on May 10, 2019, which claims priority to U.S.Provisional Application No. 62/690,021, entitled “CONFLICT AVOIDANCE INRANDOM ACCESS CHANNEL (RACH) RESOURCES IN INTEGRATED ACCESS AND BACKHAUL(IAB) NETWORKS”, filed on Jun. 26, 2018, which are expresslyincorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure relate to wireless communications, andmore particularly, to avoiding conflicts of resources assigned to one ormore signals with resources assigned to Random Access Channel (RACH) inan Integrated Access and Backhaul (IAB) network.

DESCRIPTION OF RELATED ART

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,broadcasts, etc. These wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power, etc.). Examples of such multiple-access systems include3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)systems, LTE Advanced (LTE-A) systems, code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems, to name a few.

In some examples, a wireless multiple-access communication system mayinclude a number of base stations (BSs), which are each capable ofsimultaneously supporting communication for multiple communicationdevices, otherwise known as user equipments (UEs). In an LTE or LTE-Anetwork, a set of one or more base stations may define an eNodeB (eNB).In other examples (e.g., in a next generation, a new radio (NR), or5^(th) generation (5G) network), a wireless multiple accesscommunication system may include a number of distributed units (DUs)(e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smartradio heads (SRHs), transmission reception points (TRPs), etc.) incommunication with a number of central units (CUs) (e.g., central nodes(CNs), access node controllers (ANCs), etc.), where a set of one or moredistributed units, in communication with a central unit, may define anaccess node (e.g., which may be referred to as a base station, 5G NB,next generation NodeB (gNB or gNodeB), TRP, etc.). A base station ordistributed unit may communicate with a set of UEs on downlink channels(e.g., for transmissions from a base station or to a UE) and uplinkchannels (e.g., for transmissions from a UE to a base station ordistributed unit).

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. New Radio (NR) (e.g., 5G) is an exampleof an emerging telecommunication standard. NR is a set of enhancementsto the LTE mobile standard promulgated by 3GPP. It is designed to bettersupport mobile broadband Internet access by improving spectralefficiency, lowering costs, improving services, making use of newspectrum, and better integrating with other open standards using OFDMAwith a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL).To these ends, NR supports beamforming, multiple-input multiple-output(MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in NR and LTEtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

BRIEF SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects provide a method for wireless communication. The methodgenerally includes obtaining a first configuration of a first set ofsignals configured for a first Base Station (BS); obtaining a secondconfiguration of a second set of signals configured for a second BS;determining, based on the obtained first and second configurations, aRandom Access Channel (RACH) configuration for the first BS forperforming a RACH procedure with the second BS over a wireless backhaullink, wherein one or more Physical RACH (PRACH) occasions according tothe determined RACH configuration do not conflict with resources usedfor at least one of the first set of signals or the second set ofsignals; and communicating the determined RACH configuration to thesecond BS, wherein the second BS transmits a RACH signal to the first BSbased on the determined RACH configuration.

Certain aspects of the present disclosure provide a method for wirelesscommunication by a first Base Station (BS). The method generallyincludes transmitting a random access channel (RACH) configuration to asecond BS; receiving a configuration of a set of signals configured forthe second BS; determining as invalid, based on the receivedconfiguration, one or more Physical RACH (PRACH) occasions according tothe RACH configuration of the first BS that conflict with resources usedfor at least one of the set of signals configured for the second BS; andreceiving a RACH preamble from the second BS on a PRACH occasion notconflicting with resources used for at least one of the set of signalsconfigured for the second BS.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a first Base Station (BS). The method generallyincludes obtaining a Random Access Channel (RACH) configuration to beused by a second BS for transmitting a RACH signal on at least onePhysical RACH (PRACH) occasion according to the RACH configuration;determining at least one symbol after the at least one PRACH occasion asinvalid for one or more downlink transmissions by the first BS to avoidinterference from the RACH signal used by the second BS; andtransmitting downlink signals based on the determination.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a User Equipment (UE) served by a first Base Station(BS). The method generally includes obtaining a Random Access Channel(RACH) configuration to be used by a second BS for transmitting a RACHsignal on at least one Physical RACH (PRACH) occasion according to theRACH configuration; determining at least one symbol after the at leastone PRACH occasion as invalid for one or more downlink transmissions bythe first BS to the UE, to avoid interference to the downlinktransmissions from the RACH signal used by the second BS; and receivingthe downlink transmissions on one or more downlink symbols notdetermined as invalid.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe appended drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the drawings. It is to be noted, however, thatthe appended drawings illustrate only certain typical aspects of thisdisclosure and are therefore not to be considered limiting of its scope,for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram illustrating an example logical architectureof a distributed radio access network (RAN), in accordance with certainaspects of the present disclosure.

FIG. 3 is a diagram illustrating an example physical architecture of adistributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 4 is a block diagram conceptually illustrating a design of anexample base station (BS) and user equipment (UE), in accordance withcertain aspects of the present disclosure.

FIG. 5 is a diagram showing examples for implementing a communicationprotocol stack, in accordance with certain aspects of the presentdisclosure.

FIG. 6 illustrates an example of a frame format for a new radio (NR)system, in accordance with certain aspects of the present disclosure.

FIG. 7 illustrates an example IAB network 700 in which aspects of thepresent disclosure may be practiced.

FIG. 8 illustrates example operations 800 performed by a network node oran IAB node for avoiding conflicts between RACH signals and othersignals in an IAB network, in accordance with certain aspects of thepresent disclosure.

FIG. 9 illustrates example operations 900 performed by a first BS (e.g.,a target ANF node) for avoiding conflicts between RACH signals and othersignals in an IAB network, in accordance with certain aspects of thepresent disclosure.

FIG. 10 illustrates example operations 1000 performed by a first BS(e.g, IAB node), for avoiding interference from RACH signals transmittedin a neighboring backhaul link, in accordance with certain aspects ofthe present disclosure.

FIG. 11 illustrates example operations 1100 performed by a UE served bythe first BS of FIG. 10 , for avoiding interference from RACH signalstransmitted in a neighboring backhaul link, in accordance with certainaspects of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

With recent advancement in mmWave communication with highly directionalbeamforming, it is possible to replace the so called last-mile fibersfor small BSs by establishing fixed mmWave backhaul links between thesmall BS and the macro BS equipped with fiber backhaul, also known asthe anchored BS, thereby achieving Gigabits per second (Gbps) rangedata-rate over backhaul links. While mmWave fixed wireless backhaul istargeted to be a part of the first phase of the commercial rollout of5G, 3GPP is proposing an integrated access and backhaul (IAB) networkwhere the anchor BSs will use same spectral resources and infrastructureof mmWave transmission to serve cellular users in access as well as thesmall BSs in backhaul. An IAB network uses 5G mmWave communication tosupport an access network including access links between access nodes(ANs) and UEs, as well as a backhaul network including wireless backhaullinks between ANs of the IAB network. In a typical IAB network resources(e.g., time and/or frequency resources) are shared between the accessand backhaul networks/links.

In certain aspects, a gNB selects a Random Access Channel (RACH)configuration based on a DL/UL pattern configured for the gNB, such thatthere are sufficient Physical RACH (PRACH) resources (e.g., PRACHoccasions) assigned to the uplink and flexible portions (e.g., UL andflexible symbols) of the DL/UL pattern. Different gNBs may havedifferent configured DL/UL patterns resulting in different gNBsselecting different RACH configurations. In certain aspects, when a UEfunctionality of an IAB node (hereinafter referred to as UEF node) isbeing handed over from an access node functionality of a source IAB node(hereinafter referred as source ANF node) to an access nodefunctionality of a target IAB node (hereinafter referred as target ANFnode), the UEF node, as part of the handover, needs to transmit a RACHpreamble to the target ANF node on PRACH resources configured by thetarget ANF node, in order to initiate a RACH procedure with the targetANF node. However, the UEF node and the target ANF node may havedifferent configured UL/DL patterns, and the RACH configuration of thetarget ANF node may not be suitable for the UEF node. For example one ormore PRACH occasions according to the RACH configuration of the targetANF node may conflict with resources (e.g., time and/or frequencyresources) assigned for other signals transmitted by and/or received bythe UEF node on an access link or backhaul link. In an aspect, each ofthe source and target ANF nodes may include an IAB donor node.

Certain aspects of the present disclosure describe techniques foravoiding conflicts of resources assigned to one or more signals withresources assigned to a Random Access Channel (RACH) in an IntegratedAccess and Backhaul (IAB) network.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in some other examples. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition to,or other than, the various aspects of the disclosure set forth herein.It should be understood that any aspect of the disclosure disclosedherein may be embodied by one or more elements of a claim. The word“exemplary” is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

The techniques described herein may be used for various wirelesscommunication technologies, such as LTE, CDMA, TDMA, FDMA, OFDMA,SC-FDMA and other networks. The terms “network” and “system” are oftenused interchangeably. A CDMA network may implement a radio technologysuch as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRAincludes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implementa radio technology such as Global System for Mobile Communications(GSM). An OFDMA network may implement a radio technology such as NR(e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRAand E-UTRA are part of Universal Mobile Telecommunication System (UMTS).

New Radio (NR) is an emerging wireless communications technology underdevelopment in conjunction with the 5G Technology Forum (5GTF). 3GPPLong Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTSthat use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, while aspects may be describedherein using terminology commonly associated with 3G and/or 4G wirelesstechnologies, aspects of the present disclosure can be applied in othergeneration-based communication systems, such as 5G and later, includingNR technologies.

New radio (NR) access (e.g., 5G technology) may support various wirelesscommunication services, such as enhanced mobile broadband (eMBB)targeting wide bandwidth (e.g., 80 MHz or beyond), millimeter wave (mmW)targeting high carrier frequency (e.g., 25 GHz or beyond), massivemachine type communications MTC (mMTC) targeting non-backward compatibleMTC techniques, and/or mission critical targeting ultra-reliablelow-latency communications (URLLC). These services may include latencyand reliability requirements. These services may also have differenttransmission time intervals (TTI) to meet respective quality of service(QoS) requirements. In addition, these services may co-exist in the samesubframe.

Example Wireless Communications System

FIG. 1 illustrates an example wireless communication network 100 inwhich aspects of the present disclosure may be performed. For example,the wireless communication network 100 may be a New Radio (NR) or 5Gnetwork. In an aspect, one or more base stations (BSs) 110 and one ormore UEs 120 may form an Integrated Access and Backhaul (IAB) network.In an aspect, as shown in FIG. 1 , each of the BSs 110 may be configuredto perform operations related to avoiding conflicts between RACH signalsand other signals in an IAB network, according to aspects describedherein. In an aspect, each of the BSs 110 may also be configured toperform operations related to avoiding interference from RACH signalstransmitted in a neighboring backhaul link in an IAB network, accordingto aspects described herein. In an aspect, as shown in FIG. 1 , each ofthe User Equipments (UEs) 120 may be configured to perform operationsrelated to avoiding interference from RACH signals transmitted in aneighboring backhaul link in an IAB network according to aspectsdescribed herein.

As illustrated in FIG. 1 , the wireless network 100 may include a numberof base stations (BSs) 110 and other network entities. A BS may be astation that communicates with user equipments (UEs). Each BS 110 mayprovide communication coverage for a particular geographic area. In3GPP, the term “cell” can refer to a coverage area of a Node B (NB)and/or a Node B subsystem serving this coverage area, depending on thecontext in which the term is used. In NR systems, the term “cell” andnext generation NodeB (gNB), new radio base station (NR BS), 5G NB,access point (AP), or transmission reception point (TRP) may beinterchangeable. In some examples, a cell may not necessarily bestationary, and the geographic area of the cell may move according tothe location of a mobile BS. In some examples, the base stations may beinterconnected to one another and/or to one or more other base stationsor network nodes (not shown) in wireless communication network 100through various types of backhaul interfaces, such as a direct physicalconnection, a wireless connection, a virtual network, or the like usingany suitable transport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a subcarrier, afrequency channel, a tone, a subband, etc. Each frequency may support asingle RAT in a given geographic area in order to avoid interferencebetween wireless networks of different RATs. In some cases, NR or 5G RATnetworks may be deployed.

A base station (BS) may provide communication coverage for a macro cell,a pico cell, a femto cell, and/or other types of cells. A macro cell maycover a relatively large geographic area (e.g., several kilometers inradius) and may allow unrestricted access by UEs with servicesubscription. A pico cell may cover a relatively small geographic areaand may allow unrestricted access by UEs with service subscription. Afemto cell may cover a relatively small geographic area (e.g., a home)and may allow restricted access by UEs having an association with thefemto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for usersin the home, etc.). A BS for a macro cell may be referred to as a macroBS. A BS for a pico cell may be referred to as a pico BS. A BS for afemto cell may be referred to as a femto BS or a home BS. In the exampleshown in FIG. 1 , the BSs 110 a, 110 b and 110 c may be macro BSs forthe macro cells 102 a, 102 b and 102 c, respectively. The BS 110 x maybe a pico BS for a pico cell 102 x. The BSs 110 y and 110 z may be femtoBSs for the femto cells 102 y and 102 z, respectively. A BS may supportone or multiple (e.g., three) cells.

Wireless communication network 100 may also include relay stations. Arelay station is a station that receives a transmission of data and/orother information from an upstream station (e.g., a BS or a UE) andsends a transmission of the data and/or other information to adownstream station (e.g., a UE or a BS). A relay station may also be aUE that relays transmissions for other UEs. In the example shown in FIG.1 , a relay station 110 r may communicate with the BS 110 a and a UE 120r in order to facilitate communication between the BS 110 a and the UE120 r. A relay station may also be referred to as a relay BS, a relay,etc.

Wireless network 100 may be a heterogeneous network that includes BSs ofdifferent types, e.g., macro BS, pico BS, femto BS, relays, etc. Thesedifferent types of BSs may have different transmit power levels,different coverage areas, and different impact on interference in thewireless network 100. For example, macro BS may have a high transmitpower level (e.g., 20 Watts) whereas pico BS, femto BS, and relays mayhave a lower transmit power level (e.g., 1 Watt).

Wireless communication network 100 may support synchronous orasynchronous operation. For synchronous operation, the BSs may havesimilar frame timing, and transmissions from different BSs may beapproximately aligned in time. For asynchronous operation, the BSs mayhave different frame timing, and transmissions from different BSs maynot be aligned in time. The techniques described herein may be used forboth synchronous and asynchronous operation.

A network controller 130 may couple to a set of BSs and providecoordination and control for these BSs. The network controller 130 maycommunicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another (e.g., directly or indirectly) via wirelessor wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless network 100, and each UE may be stationary or mobile. A UE mayalso be referred to as a mobile station, a terminal, an access terminal,a subscriber unit, a station, a Customer Premises Equipment (CPE), acellular phone, a smart phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet computer, a camera, a gaming device, a netbook, a smartbook, anultrabook, an appliance, a medical device or medical equipment, abiometric sensor/device, a wearable device such as a smart watch, smartclothing, smart glasses, a smart wrist band, smart jewelry (e.g., asmart ring, a smart bracelet, etc.), an entertainment device (e.g., amusic device, a video device, a satellite radio, etc.), a vehicularcomponent or sensor, a smart meter/sensor, industrial manufacturingequipment, a global positioning system device, or any other suitabledevice that is configured to communicate via a wireless or wired medium.Some UEs may be considered machine-type communication (MTC) devices orevolved MTC (eMTC) devices. MTC and eMTC UEs include, for example,robots, drones, remote devices, sensors, meters, monitors, locationtags, etc., that may communicate with a BS, another device (e.g., remotedevice), or some other entity. A wireless node may provide, for example,connectivity for or to a network (e.g., a wide area network such asInternet or a cellular network) via a wired or wireless communicationlink. Some UEs may be considered Internet-of-Things (IoT) devices, whichmay be narrowband IoT (NB-IoT) devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, etc. Each subcarriermay be modulated with data. In general, modulation symbols are sent inthe frequency domain with OFDM and in the time domain with SC-FDM. Thespacing between adjacent subcarriers may be fixed, and the total numberof subcarriers (K) may be dependent on the system bandwidth. Forexample, the spacing of the subcarriers may be 15 kHz and the minimumresource allocation (called a “resource block” (RB)) may be 12subcarriers (or 180 kHz). Consequently, the nominal Fast FourierTransfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 forsystem bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz),respectively. The system bandwidth may also be partitioned intosubbands. For example, a subband may cover 1.08 MHz (i.e., 6 resourceblocks), and there may be 1, 2, 4, 8, or 16 subbands for systembandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR. NR may utilizeOFDM with a CP on the uplink and downlink and include support forhalf-duplex operation using TDD. Beamforming may be supported and beamdirection may be dynamically configured. MIMO transmissions withprecoding may also be supported. MIMO configurations in the DL maysupport up to 8 transmit antennas with multi-layer DL transmissions upto 8 streams and up to 2 streams per UE. Multi-layer transmissions withup to 2 streams per UE may be supported. Aggregation of multiple cellsmay be supported with up to 8 serving cells.

In some examples, access to the air interface may be scheduled, whereina. A scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. The scheduling entity may be responsible for scheduling,assigning, reconfiguring, and releasing resources for one or moresubordinate entities. That is, for scheduled communication, subordinateentities utilize resources allocated by the scheduling entity. Basestations are not the only entities that may function as a schedulingentity. In some examples, a UE may function as a scheduling entity andmay schedule resources for one or more subordinate entities (e.g., oneor more other UEs), and the other UEs may utilize the resourcesscheduled by the UE for wireless communication. In some examples, a UEmay function as a scheduling entity in a peer-to-peer (P2P) network,and/or in a mesh network. In a mesh network example, UEs may communicatedirectly with one another in addition to communicating with a schedulingentity.

In FIG. 1 , a solid line with double arrows indicates desiredtransmissions between a UE and a serving BS, which is a BS designated toserve the UE on the downlink and/or uplink. A finely dashed line withdouble arrows indicates interfering transmissions between a UE and a BS.

FIG. 2 illustrates an example logical architecture of a distributedRadio Access Network (RAN) 200, which may be implemented in the wirelesscommunication network 100 illustrated in FIG. 1 . A 5G access node 206may include an access node controller (ANC) 202. ANC 202 may be acentral unit (CU) of the distributed RAN 200. The backhaul interface tothe Next Generation Core Network (NG-CN) 204 may terminate at ANC 202.The backhaul interface to neighboring next generation access Nodes(NG-ANs) 210 may terminate at ANC 202. ANC 202 may include one or moretransmission reception points (TRPs) 208 (e.g., cells, BSs, gNBs, etc.).

In an aspect, the 5G access node 206 may be part of an Integrated Accessand Backhaul (IAB) network. In an aspect, at least one of the NG-CN 204or the 5G access node 206 may be configured to perform operationsrelated to avoiding conflicts between RACH signals and other signals inan IAB network, according to aspects described herein. In an aspect, 5Gaccess node 206 may also be configured to perform operations related toavoiding interference from RACH signals transmitted in a neighboringbackhaul link in an IAB network, according to aspects described herein.

The TRPs 208 may be a distributed unit (DU). TRPs 208 may be connectedto a single ANC (e.g., ANC 202) or more than one ANC (not illustrated).For example, for RAN sharing, radio as a service (RaaS), and servicespecific AND deployments, TRPs 208 may be connected to more than oneANC. TRPs 208 may each include one or more antenna ports. TRPs 208 maybe configured to individually (e.g., dynamic selection) or jointly(e.g., joint transmission) serve traffic to a UE.

The logical architecture of distributed RAN 200 may support fronthaulingsolutions across different deployment types. For example, the logicalarchitecture may be based on transmit network capabilities (e.g.,bandwidth, latency, and/or jitter).

The logical architecture of distributed RAN 200 may share featuresand/or components with LTE. For example, next generation access node(NG-AN) 210 may support dual connectivity with NR and may share a commonfronthaul for LTE and NR.

The logical architecture of distributed RAN 200 may enable cooperationbetween and among TRPs 208, for example, within a TRP and/or across TRPsvia ANC 202. An inter-TRP interface may not be used.

Logical functions may be dynamically distributed in the logicalarchitecture of distributed RAN 200. As will be described in more detailwith reference to FIG. 5 , the Radio Resource Control (RRC) layer,Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC)layer, Medium Access Control (MAC) layer, and a Physical (PHY) layersmay be adaptably placed at the DU (e.g., TRP 208) or CU (e.g., ANC 202).

FIG. 3 illustrates an example physical architecture of a distributedRadio Access Network (RAN) 300, according to aspects of the presentdisclosure. A centralized core network unit (C-CU) 302 may host corenetwork functions. C-CU 302 may be centrally deployed. C-CU 302functionality may be offloaded (e.g., to advanced wireless services(AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions.Optionally, the C-RU 304 may host core network functions locally. TheC-RU 304 may have distributed deployment. The C-RU 304 may be close tothe network edge.

A DU 306 may host one or more TRPs (Edge Node (EN), an Edge Unit (EU), aRadio Head (RH), a Smart Radio Head (SRH), or the like). The DU may belocated at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of BS 110 and UE 120 (as depictedin FIG. 1 ), which may be used to implement aspects of the presentdisclosure. For example, antennas 452, processors 466, 458, 464, and/orcontroller/processor 480 of the UE 120 and/or antennas 434, processors420, 460, 438, and/or controller/processor 440 of the BS 110 may be usedto perform the various techniques and methods described herein. In anaspect, the BS 110 and the UE 120 may be part of an Integrated Accessand Backhaul (IAB) network. In an aspect, the BS 110 may be configuredto perform operations related to avoiding conflicts between RACH signalsand other signals in an IAB network, according to aspects describedherein. In an aspect, the BS 110 may also be configured to performoperations related to avoiding interference from RACH signalstransmitted in a neighboring backhaul link in an IAB network, accordingto aspects described herein. In an aspect, the UE 120 may be configuredto perform operations related to avoiding interference from RACH signalstransmitted in a neighboring backhaul link in an IAB network accordingto aspects described herein.

At the BS 110, a transmit processor 420 may receive data from a datasource 412 and control information from a controller/processor 440. Thecontrol information may be for the physical broadcast channel (PBCH),physical control format indicator channel (PCFICH), physical hybrid ARQindicator channel (PHICH), physical downlink control channel (PDCCH),group common PDCCH (GC PDCCH), etc. The data may be for the physicaldownlink shared channel (PDSCH), etc. The processor 420 may process(e.g., encode and symbol map) the data and control information to obtaindata symbols and control symbols, respectively. The processor 420 mayalso generate reference symbols, e.g., for the primary synchronizationsignal (PSS), secondary synchronization signal (SSS), and cell-specificreference signal (CRS). A transmit (TX) multiple-input multiple-output(MIMO) processor 430 may perform spatial processing (e.g., precoding) onthe data symbols, the control symbols, and/or the reference symbols, ifapplicable, and may provide output symbol streams to the modulators(MODs) 432 a through 432 t. Each modulator 432 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. Downlink signals from modulators 432 a through 432 tmay be transmitted via the antennas 434 a through 434 t, respectively.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) in transceivers 454 a through 454 r,respectively. Each demodulator 454 may condition (e.g., filter, amplify,downconvert, and digitize) a respective received signal to obtain inputsamples. Each demodulator may further process the input samples (e.g.,for OFDM, etc.) to obtain received symbols. A MIMO detector 456 mayobtain received symbols from all the demodulators 454 a through 454 r,perform MIMO detection on the received symbols if applicable, andprovide detected symbols. A receive processor 458 may process (e.g.,demodulate, deinterleave, and decode) the detected symbols, providedecoded data for the UE 120 to a data sink 460, and provide decodedcontrol information to a controller/processor 480.

On the uplink, at UE 120, a transmit processor 464 may receive andprocess data (e.g., for the physical uplink shared channel (PUSCH)) froma data source 462 and control information (e.g., for the physical uplinkcontrol channel (PUCCH) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a reference signal(e.g., for the sounding reference signal (SRS)). The symbols from thetransmit processor 464 may be precoded by a TX MIMO processor 466 ifapplicable, further processed by the demodulators in transceivers 454 athrough 454 r (e.g., for SC-FDM, etc.), and transmitted to the basestation 110. At the BS 110, the uplink signals from the UE 120 may bereceived by the antennas 434, processed by the modulators 432, detectedby a MIMO detector 436 if applicable, and further processed by a receiveprocessor 438 to obtain decoded data and control information sent by theUE 120. The receive processor 438 may provide the decoded data to a datasink 439 and the decoded control information to the controller/processor440.

The controllers/processors 440 and 480 may direct the operation at thebase station 110 and the UE 120, respectively. The processor 440 and/orother processors and modules at the BS 110 may perform or direct theexecution of processes for the techniques described herein. The memories442 and 482 may store data and program codes for BS 110 and UE 120,respectively. A scheduler 444 may schedule UEs for data transmission onthe downlink and/or uplink.

FIG. 5 illustrates a diagram 500 showing examples for implementing acommunications protocol stack, according to aspects of the presentdisclosure. The illustrated communications protocol stacks may beimplemented by devices operating in a wireless communication system,such as a 5G system (e.g., a system that supports uplink-basedmobility). Diagram 500 illustrates a communications protocol stackincluding a Radio Resource Control (RRC) layer 510, a Packet DataConvergence Protocol (PDCP) layer 515, a Radio Link Control (RLC) layer520, a Medium Access Control (MAC) layer 525, and a Physical (PHY) layer530. In various examples, the layers of a protocol stack may beimplemented as separate modules of software, portions of a processor orASIC, portions of non-collocated devices connected by a communicationslink, or various combinations thereof. Collocated and non-collocatedimplementations may be used, for example, in a protocol stack for anetwork access device (e.g., ANs, CUs, and/or DUs) or a UE.

A first option 505-a shows a split implementation of a protocol stack,in which implementation of the protocol stack is split between acentralized network access device (e.g., an ANC 202 in FIG. 2 ) anddistributed network access device (e.g., DU 208 in FIG. 2 ). In thefirst option 505-a, an RRC layer 510 and a PDCP layer 515 may beimplemented by the central unit, and an RLC layer 520, a MAC layer 525,and a PHY layer 530 may be implemented by the DU. In various examplesthe CU and the DU may be collocated or non-collocated. The first option505-a may be useful in a macro cell, micro cell, or pico celldeployment.

A second option 505-b shows a unified implementation of a protocolstack, in which the protocol stack is implemented in a single networkaccess device. In the second option, RRC layer 510, PDCP layer 515, RLClayer 520, MAC layer 525, and PHY layer 530 may each be implemented bythe AN. The second option 505-b may be useful in, for example, a femtocell deployment.

Regardless of whether a network access device implements part or all ofa protocol stack, a UE may implement an entire protocol stack as shownin 505-c (e.g., the RRC layer 510, the PDCP layer 515, the RLC layer520, the MAC layer 525, and the PHY layer 530).

In LTE, the basic transmission time interval (TTI) or packet duration isthe 1 ms subframe. In NR, a subframe is still 1 ms, but the basic TTI isreferred to as a slot. A subframe contains a variable number of slots(e.g., 1, 2, 4, 8, 16, . . . slots) depending on the subcarrier spacing.The NR RB is 12 consecutive frequency subcarriers. NR may support a basesubcarrier spacing of 15 KHz and other subcarrier spacing may be definedwith respect to the base subcarrier spacing, for example, 30 kHz, 60kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with thesubcarrier spacing. The CP length also depends on the subcarrierspacing.

FIG. 6 is a diagram showing an example of a frame format 600 for NR. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 ms) and may be partitioned into 10subframes, each of 1 ms, with indices of 0 through 9. Each subframe mayinclude a variable number of slots depending on the subcarrier spacing.Each slot may include a variable number of symbol periods (e.g., 7 or 14symbols) depending on the subcarrier spacing. The symbol periods in eachslot may be assigned indices. A mini-slot is a subslot structure (e.g.,2, 3, or 4 symbols).

Each symbol in a slot may indicate a link direction (e.g., DL, UL, orflexible) for data transmission and the link direction for each subframemay be dynamically switched. The link directions may be based on theslot format. Each slot may include DL/UL data as well as DL/UL controlinformation.

In NR, a synchronization signal (SS) block is transmitted. The SS blockincludes a PSS, a SSS, and a two symbol PBCH. The SS block can betransmitted in a fixed slot location, such as the symbols 0-3 as shownin FIG. 6 . The PSS and SSS may be used by UEs for cell search andacquisition. The PSS may provide half-frame timing, the SS may providethe CP length and frame timing. The PSS and SSS may provide the cellidentity. The PBCH carries some basic system information, such asdownlink system bandwidth, timing information within radio frame, SSburst set periodicity, system frame number, etc. The SS blocks may beorganized into SS bursts to support beam sweeping. Further systeminformation such as, remaining minimum system information (RMSI), systeminformation blocks (SIBs), other system information (OSI) can betransmitted on a physical downlink shared channel (PDSCH) in certainsubframes.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including aconfiguration associated with transmitting pilots using a dedicated setof resources (e.g., a radio resource control (RRC) dedicated state,etc.) or a configuration associated with transmitting pilots using acommon set of resources (e.g., an RRC common state, etc.). Whenoperating in the RRC dedicated state, the UE may select a dedicated setof resources for transmitting a pilot signal to a network. Whenoperating in the RRC common state, the UE may select a common set ofresources for transmitting a pilot signal to the network. In eithercase, a pilot signal transmitted by the UE may be received by one ormore network access devices, such as an AN, or a DU, or portionsthereof. Each receiving network access device may be configured toreceive and measure pilot signals transmitted on the common set ofresources, and also receive and measure pilot signals transmitted ondedicated sets of resources allocated to the UEs for which the networkaccess device is a member of a monitoring set of network access devicesfor the UE. One or more of the receiving network access devices, or a CUto which receiving network access device(s) transmit the measurements ofthe pilot signals, may use the measurements to identify serving cellsfor the UEs, or to initiate a change of serving cell for one or more ofthe UEs.

Example Conflict Avoidance with Rach Resources in an IAB Network

With the exponential rise in data-demand far exceeding the capacity ofthe traditional macro-only cellular network operating in sub-6 GHzbands, network densification using mmWave base stations (BSs) isbecoming a major driving technology for the 5G wireless evolution. Whileheterogeneous cellular networks (HetNets) with low power small BSsoverlaid with traditional macro BSs improve the spectral efficiency ofthe access link (the link between a user and its serving BS), mmWavecommunication may further boost the data-rate by offering highbandwidth. That said, the HetNet concept never really turned into amassive real-time deployment since the existing high-speed optical fiberbackhaul network that connects the BSs to the network core is notscalable to the extent of ultra-densification envisioned for smallcells. However, with recent advancement in mmWave communication withhighly directional beamforming, it is possible to replace the so calledlast-mile fibers for small BSs by establishing fixed mmWave wirelessbackhaul links between the small BS and a corresponding macro BSequipped with fiber backhaul, also known as the anchored BS, therebyachieving Gigabits per second (Gbps) range data-rate over the backhaullinks. While mmWave fixed wireless backhaul is targeted to be a part ofthe first phase of the commercial rollout of 5G, 3GPP is proposing anintegrated access and backhaul (IAB) network where the anchor BSs willuse same spectral resources and infrastructure of mmWave transmission toserve cellular users in access as well as the small BSs in backhaul.

An IAB network uses 5G mmWave communication to support an access networkincluding access links between access nodes (ANs) and UEs, as well as abackhaul network including wireless backhaul links between ANs of theIAB network. In a typical IAB, network resources (e.g., time and/orfrequency resources) are shared between the access and backhaulnetworks/links.

FIG. 7 illustrates an example IAB network 700 in which aspects of thepresent disclosure may be practiced. As shown, the IAB network 700includes one or more IAB donor nodes (e.g., 702 a and 702 b). An IABdonor node is a Radio Access Network (RAN) node (e.g., base station/gNBthat terminates the NR Ng interface with the core network (e.g, nextgeneration NG core)) and is generally connected to the core network viaa wireline backhaul link. An IAB donor node 702 may also be referred toas an IAB anchor node and may include an IAB Central Unit (e.g., NR CU)or an IAB Distributed Unit (e.g, NR DU). The IAB network 700 furtherincludes one or more non-donor IAB nodes (e.g., 704 a-704 g). Each IABnode (including donor and non-donor IAB nodes) may serve one or more UEs(e.g., 706 a-706 h) connected to the IAB node. As shown, the IAB nodes,including the donor IAB nodes 702, may be connected via NR wirelessbackhaul links or backup NR wireless backhaul links. Each IAB nodeconnects to its served UEs via respective access links. Each IAB node isa RAN node (e.g., base station/gNB) that provides IAB functionality withtwo roles including an access node function (AN-F) and a UE function(UE-F). The AN-F of an IAB node is generally responsible for schedulingUEs (e.g., served by the IAB node) and other IAB nodes (e.g., that areconnected as child nodes to the IAB node). The AN-F also controls bothaccess and backhaul links under its coverage. The UE-F of an IAB node iscontrolled and scheduled by an IAB donor node or another IAB node as itsparent IAB node. In an aspect, the IAB donor nodes 702 only include AN-Fand no UE-F.

As noted above, both access links and wireless backhaul links use thesame mmWave framework and share time and/or frequency resources.

It may be noted that the terms “configuring” and “scheduling” areinterchangeably used throughout this disclosure.

In certain aspects, a gNB selects a Random Access Channel (RACH)configuration based on a DL/UL pattern configured for the gNB, such thatthere are sufficient Physical RACH (PRACH) resources (e.g., PRACHoccasions) assigned to the uplink and flexible portions (e.g., UL andflexible symbols) of the DL/UL pattern. Different gNBs may havedifferent configured DL/UL patterns resulting in different gNBsselecting different RACH configurations. In certain aspects, when a UEfunctionality of an IAB node (hereinafter referred to as UEF node) isbeing handed over from an access node functionality of a source IAB node(hereinafter referred as source ANF node) to an access nodefunctionality of a target IAB node (hereinafter referred as target ANFnode), the UEF node, as part of the handover, needs to transmit a RACHpreamble to the target ANF node on PRACH resources configured by thetarget ANF node, in order to initiate a RACH procedure with the targetANF node. However, the UEF node and the target ANF node may havedifferent configured UL/DL patterns, and the RACH configuration of thetarget ANF node may not be suitable for the UEF node. For example one ormore PRACH occasions according to the RACH configuration of the targetANF node may conflict with resources (e.g, time and/or frequencyresources) assigned for other signals transmitted by and/or received bythe UEF node on an access link or backhaul link. In an aspect, each ofthe source and target ANF nodes may include an IAB donor node.

In an aspect, these other signals may include uplink and/or downlinksignals associated with the UEF node on an access link and/or a backhaullink, including at least one of uplink transmissions, primarysynchronization signals (PSS), secondary synchronization signals (SSS),PBCH signals, remaining system information, other system information,random access response from one or more UEs served by the UEF node,Channel State Information Reference Signals (CSI-RS), or paging signals.

In an example scenario, the UEF node 704 f may receive an indication ofa handover from a current source ANF node 704 b to a target ANF node 704c. Target ANF node 704 c and UEF node 704 f may have different UL/DLpatterns and the RACH configuration of the target ANF node 704 c (e.g.,based on its UL/DL pattern) may not be suitable for the UEF node 704 f.In an aspect, all IAB nodes 704 managed by a particular IAB donor node702 may have their RACH configurations configured such that theirrespective RACH configurations avoid conflicts with UL/DL signals ofother IAB nodes 704 managed by the same IAB donor node 702, for example,regardless of the UL/DL patterns of the IAB nodes 704 being the same ordifferent. However, for IAB nodes 704 that are managed by different IABdonor nodes (e.g., 702 a and 702 b) and having different UL/DL patterns,the RACH patterns of a first IAB node managed by a first IAB donor nodemay not be configured to avoid conflicts with other signals of a secondIAB node managed by a second IAB donor node.

Referring to the above example scenario, UEF node 704 f may be managedby the IAB donor node 702 a and the ANF node 704 c may be managed by theIAB donor node 702 b. As a result, the RACH configuration of the ANFnode 704 c may not be configured to avoid conflicts with other UL/DLsignals associated with the UEF node 704 f. In this context, a RACHpreamble transmitted on one or more PRACH occasion according to the RACHconfiguration of the ANF node 704 c may conflict with one or more othersignals associated with the UEF node 704 f.

In an aspect, the UEF node 704 f may support only one Radio Frequency(RF) chain, and as a result may transmit only or receive only at onetime. Thus, if the ANF node 704 c and UEF node 704 f have differentconfigured UL/DL patterns, one or more UL occasions according to theUL/DL pattern of the ANF node 704 c may conflict with UL occasionsaccording to the UL/DL pattern of the UEF node 704 f. For example, whenthe UEF 704 f node may be required to transmit a RACH signal to the ANFnode 704 c according to the UL/DL patter of the ANF node 704 c, the UEF704 f node may need to monitor UL signals at the same time from itsserved UEs according to its own UL/DL pattern. Thus, one or more PRACHoccasions configured by the ANF node 704 c may conflict with othersignals scheduled by the UEF node 704 f (e.g., on an access link orbackhaul link) at the same time.

Certain aspects of the present disclosure describe techniques foravoiding conflicts of resources assigned to one or more signals withresources assigned to a Random Access Channel (RACH) in an IntegratedAccess and Backhaul (IAB) network.

In certain aspects, for the example scenario discussed above, the RACHconfiguration of the target ANF node 704 c may be adjusted based on aconfiguration of signals of the UEF node 704 f, to not conflict with thesignals of the UEF node.

FIG. 8 illustrates example operations 800 performed by a network node oran IAB node for avoiding conflicts between RACH signals and othersignals in an IAB network, in accordance with certain aspects of thepresent disclosure.

Operations 800 begin, at 802, by obtaining a first configuration of afirst set of signals configured by a first BS.

At 804, a second configuration is obtained of a second set of signalsconfigured for a second BS.

At 806, a RACH configuration is determined for the first BS, based onthe obtained first and second configurations, for performing a RACHprocedure with the second BS over a wireless backhaul link, wherein oneor more PRACH occasions according to the determined RACH configurationdo not conflict with resources used for at least one of the first set ofsignals or the second set of signals.

In an aspect, the first BS includes a target ANF node and the second BSincludes a UEF node, wherein the UEF node is attempting to handover froma source ANF node to the target ANF node. In an aspect, the first andsecond set of signals includes at least one of uplink transmissions, aprimary synchronization signal, a secondary synchronization signal, aPBCH signal, remaining minimum system information, other systeminformation, random access response from one or more UEs, Channel StateInformation Reference Signals (CSI-RS), or paging signals.

At 808, the determined RACH configuration is communicated to the secondBS, wherein the second BS transmits a RACH signal to the first BS basedon the determined RACH configuration. In an aspect, the RACH signalincludes a RACH preamble transmitted using one or more PRACH occasionsaccording to the determined RACH configuration.

In an aspect, the operations 800 are performed by a network nodeincluding a network core (e.g., NGC) or an IAB donor node. In thiscontext, the network may receive the first configuration of the firstset of signals from the first BS via an IAB donor node managing thefirst BS. The network may receive the second configuration of the secondset of signals from the second BS or another BS serving the second BSvia an IAB donor node. In an aspect, an IAB donor node may receive theat least one of the first or second configurations over one or more hopsusing relay IAB nodes, and may forward the received configuration to thenetwork core. In this context, the network receives the first and secondconfigurations from the first and second BSs respectively, anddetermines a RACH configuration for the RACH procedure between the firstand the second BS that does not conflict with transmissions of one ormore of the signals associated with the first and/or second BS.

In an aspect, the resources used for the first set of signals or thesecond set of signals include time resources and/or frequency resources.For example, the determined RACH configuration configures one or morePRACH occasions to not conflict in time with transmission of one or moreof the signals. That is, the PRACH occasions are configured onslots/symbols that are not scheduled for transmission of one or more ofthe other signals.

In an aspect, the second set of signals scheduled for the second BSinclude uplink transmissions by one or more UEs served by the second BSon an access link between the second BS and the one or more UEs. In thiscontext, the determined RACH configuration includes one or more PRACHoccasions that do not conflict with one or more of the UL transmissionsscheduled by the second BS.

In an aspect, the second set of signals scheduled for the second BSinclude downlink transmissions by the second BS to one or more UEsserved by the second BS on the access link between the second BS and theone or more UEs. In this context, the determined RACH configurationincludes one or more PRACH occasions that do not conflict with one ormore of the DL transmissions scheduled by the second BS. In an aspect,the second BS may support a limited set of transmit beams at one time.Thus, if the second BS is scheduled to transmit one or more signals toserved UEs using all of the limited set of beams, it may not be able totransmit a RACH preamble to the first BS. Configuration of PRACHoccasions that do not conflict with the second BS's downlinktransmissions avoids this conflict.

In an aspect, the operations 800 are performed by the first BS (e.g, thetarget IAB node). In this context, the first BS receives the secondconfiguration of the second set of signals from a source BS serving thesecond BS or from the network. Thus, the first BS receives the secondconfiguration from the second BS, and determines a RACH configurationfor the RACH procedure between the first and the second BS that does notconflict with transmissions of one or more of the signals associatedwith the first and/or second BS.

In an aspect, the second BS proactively communicates informationregarding its configuration (e.g., second configuration) to the first BSbefore the second BS attempts the RACH procedure with the first BS. Inthis context, the second BS may receive a new RACH configurationavoiding conflicts with the second BS's own transmissions, before itinitiates the RACH procedure. This may increases the chances of thesecond BS successfully completing the RACH procedure and handing over tothe first BS.

In an aspect, the second BS communicates information regarding itsconfiguration (e.g., second configuration) to the first BS only if theRACH configuration initially suggested by the first BS leads toconflicts and an unsuccessful RACH procedure with the first BS. In anaspect, the second BS transmits the second configuration to the first BSafter the second BS has unsuccessfully attempted at least one RACHprocedure with the first BS as a result of conflicting PRACH occasionswith the second set of signals. In response to the transmittedconfiguration of signals scheduled for the second BS, the second BS mayreceive a new RACH configuration from the first BS avoiding conflictswith the second BS's own transmissions. The second BS may initiate theRACH procedure based on the new RACH configuration.

In an aspect, the first BS may receive the second configuration from atleast one of directly from the second BS on a low frequency wirelesslink between the first BS and the second BS, a parent BS of the secondBS, or a donor BS of the second BS.

In an example scenario, the RACH configuration of the first BS may haveconfigured PRACH resources in every 5^(th) slot, for example, slots 4,9, 14, 19, 24 . . . 39 of the 40 slots per frame for 60 KHz carrierspacing. If the second BS has configured other signals in slots 4, 14and 24, the first BS reconfigures its RACH configuration to a RACHconfiguration that does not have PRACH occasions in slots 4, 14, and 24.

In certain aspects, the target ANF node, instead of changing its RACHconfiguration, invalidates one or more RACH occasions that conflict withone or more signals of the UEF node.

FIG. 9 illustrates example operations 900 performed by a first BS (e.g.,a target ANF node) for avoiding conflicts between RACH signals and othersignals in an IAB network, in accordance with certain aspects of thepresent disclosure.

Operations 900 begin, at 902, by transmitting a RACH configuration to asecond BS. In an aspect, the second BS is a UEF node, wherein the secondBS is to handover from a source BS (e.g., a source ANF node) to thefirst BS. In an aspect, the first BS transmits the RACH configuration tothe second BS via a parent BS (e.g., a source ANF node) of the secondBS.

At 904, the first BS receives a configuration of a set of signalsconfigured for the second BS. In an aspect, the signals include one ormore uplink and/or downlink signals configured for an access linkbetween the second BS and at least one UE or UEF node served by thesecond BS. In an aspect, the set of signals includes at least one ofuplink transmissions, a primary synchronization signal, a secondarysynchronization signal, a PBCH signal, remaining minimum systeminformation, other system information, random access response from oneor more UEs, Channel State Information Reference Signals (CSI-RS), orpaging signals.

At 906, the first BS determines as invalid, based on the receivedconfiguration, one or more PRACH occasions according to the RACHconfiguration of the first BS that conflict with resources used for atleast one of the set of signals configured for the second BS.

At 908, the first BS receives a RACH preamble from the second BS on oneor more PRACH occasions not conflicting with resources used for at leastone of the set of signals configured for the second BS. In an aspect,the resources include time and/or frequency resources.

In an aspect, the second BS is configured to determine one or more PRACHoccasions that conflict the set of signals configured for the second BSare invalid, and not transmit a RACH preamble using the invalid PRACHresources. Additionally or alternatively, the second BS may be signaled(e.g, via RRC signaling) the RACH resources that are invalid, forexample by the first BS over a low frequency link or by a parent BS(e.g., source ANF node) serving the second BS. In an aspect, once thesecond BS determines the invalid RACH resources, the second BS transmitsa RACH preamble using one or more PRACH resources not determined asinvalid.

In an example scenario, the RACH configuration of the first BS may haveconfigured PRACH resources in every 5^(th) slot, for example, slots 4,9, 14, 19, 24 . . . 39 of the 40 slots per frame for 60 KHz carrierspacing. If the second BS has configured other signals in slots 4, 14and 24, the first BS and the second BS determine that the PRACHoccasions in slots 4, 14, and 24 are invalid. The second BS may transmita RACH preamble using any of the PRACH occasions in slots 9, 19, 29 andso on.

In certain aspects, RACH transmissions in a backhaul link between twoIAB nodes may arrive at a neighboring cell after a delay. This may causeinterference to transmissions on an access link within the neighboringcell. For example, in the IAB network 700, IAB node 704 e may transmit aRACH preamble to IAB node 704 g in symbol N. However, this RACH signalmay reach the UE 706 e served by IAB node 704 c after a delay of one ormore symbols. In an aspect, while the IAB node 704 c may have scheduledits downlink signals to UE 706 e to not conflict with the RACH preamblein symbol N, the IAB node 704 c may schedule downlink signals in one ormore symbols right after the RACH preamble transmission in symbol N.However, since the RACH signal transmitted in the symbol N by IAB node704 e may reach UE 706 e one or more symbols later (e.g., symbol N+1 orlater), the RACH signal may interfere with the downlink signalstransmitted by the IAB node 704 c in one or more symbols after thesymbol N.

In certain aspects, similar to the inter cell interference case notedabove, a RACH signal transmitted by one UE in symbol N within a cell mayinterfere with downlink transmissions in symbol N+1 or later to anotherUE of the same cell or another UEF node. For example, a RACH preambletransmitted by a UE in symbol N may reach another UE of the same cellwith a delay in symbol N+1 or a little later and may interfere with adownlink signal transmitted to the other UE in symbol N+1 or a littlelater.

In certain aspects, a serving IAB node may consider X symbols after aRACH occasion invalid for transmission on one of its access links and/orbackhaul links, to avoid interference with the RACH signals transmittedduring the RACH occasion. In an aspect, the value of X may be fixed inthe specification or configured in system information or handovercommand by the network.

For example, if the serving IAB node has scheduled downlinktransmissions (e.g, PDCCH transmissions) in first few symbols of slots2, 4, 6, and 8, and knows that a PRACH occasion is configured towardsthe end of slot 3, the serving IAB node may determine the first fewsymbols of slot 4 invalid for the downlink transmissions, to avoidinterference from a RACH preamble transmitted in the PRACH occasion inslot 3.

FIG. 10 illustrates example operations 1000 performed by a first BS(e.g., IAB node), for avoiding interference from RACH signalstransmitted in a neighboring backhaul link, in accordance with certainaspects of the present disclosure.

Operations 1000 begin, at 1002, by obtaining a RACH configuration to beused for transmitting a RACH signal in a cell served by the first BS ora neighbor cell.

At 1004, the first BS determines at least one symbol after at least onePRACH occasion according to the RACH configuration as invalid for one ormore downlink transmissions by the first BS, for example, to avoidinterference to the downlink transmissions from the RACH signal. In anaspect, the RACH signal transmitted in the at least one PRACH occasionmay interfere with the downlink transmissions by the first BS in the atleast one symbol after the at least one PRACH occasion.

At 1006, the first BS transmits downlink signals based on thedetermination. For example, the first base station does not transmitdownlink signals during the determined at least symbol to one or moreUEs on respective access links or one or more other IAB nodes onrespective backhaul links, to avoid interference from the RACH signal.

In an aspect, the RACH signal is to be transmitted by a second BS (e.g.,UEF node) in the neighboring cell to a third BS using the at least onePRACH occasion. The second BS may be in a vicinity of at least one ofthe first BS, a User Equipment (UE) served by the first BS, or anotherBS (e.g., UEF node) served by the first BS.

In an aspect, the RACH signal is to be transmitted by another UE servedby the first BS using the at least one PRACH occasion.

In an aspect, the at least one symbol is a default value.

In an aspect, the at least one symbol is configured by the network andthe first BS receives the configured at least one symbol from thenetwork. In an aspect, the network configures the at least one symbolvia at least one of RMSI, OSI, DCI, RRC signaling, MAC-CE or a handovermessage.

In an aspect, the first and the second BSs are same.

FIG. 11 illustrates example operations 1100 performed by a UE served bythe first BS of FIG. 10 , for avoiding interference from RACH signalstransmitted in a neighboring backhaul link, in accordance with certainaspects of the present disclosure.

Operations 1100 begin, at 1102, by obtaining a RACH configuration to beused for transmitting a RACH signal in a cell served by the first BS ora neighboring cell.

At 1104, the UE determines at least one symbol after at least one PRACHoccasion according to the RACH configuration as invalid for one or moredownlink transmissions to be received from the first BS, for example, toavoid interference to the downlink transmissions from the RACH signal.In an aspect, the RACH signal transmitted in the at least one PRACHoccasion may interfere with the downlink transmissions by the first BSin the at least one symbol after the at least one PRACH occasion

At 1106, the UE receives the downlink transmissions based on thedetermination. For example, the UE receives the downlink transmissionson one or more downlink symbols not determined as invalid.

In an aspect, the RACH signal is to be transmitted by a second BS (e.g.,UEF node) in the neighboring cell to a third BS (e.g., ANF node) usingthe at least one PRACH occasion. In an aspect, the second BS in in avicinity of the UE.

In an aspect, the RACH signal is to be transmitted by another UE servedby the first BS using the at least one PRACH occasion.

In an aspect, the at least one symbol is a default value.

In an aspect, the at least one symbol is configured by the network andthe UE receives the configured at least one symbol from the first BS.

The methods disclosed herein comprise one or more steps or actions forachieving the methods. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112(f) unless the element is expressly recited using the phrase“means for” or, in the case of a method claim, the element is recitedusing the phrase “step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1 ), a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For example, instructions for performing the operationsdescribed herein and illustrated in FIGS. 8-11 .

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method for wireless communication by a first Base Station (BS), comprising: transmitting a random access channel (RACH) configuration to a second BS; receiving a configuration of a set of signals configured for the second BS; determining as invalid, based on the received configuration, one or more Physical RACH (PRACH) occasions according to the RACH configuration of the first BS that conflict with resources used for at least one of the set of signals configured for the second BS; and receiving a RACH preamble from the second BS on a PRACH occasion not conflicting with resources used for at least one of the set of signals configured for the second BS.
 2. The method of claim 1, wherein the transmitting comprises transmitting the RACH configuration to the second BS via a parent BS of the second BS.
 3. The method of claim 1, wherein the resources used for the at least one of the set of signals comprise time resources.
 4. The method of claim 1, wherein the resources used for the at least one of the set of signals comprise time and frequency resources.
 5. The method of claim 1, wherein the set of signals comprises one or more uplink transmissions configured for an access link between the second BS and a UE served by the second BS.
 6. The method of claim 1, wherein the set of signals comprises one or more downlink transmissions configured for an access link between the second BS and a UE served by the second BS.
 7. The method of claim 1, wherein the set of signals comprises at least one of uplink transmissions, a primary synchronization signal, a secondary synchronization signal, a PBCH signal, remaining minimum system information, other system information, random access response from one or more UEs, Channel State Information Reference Signals (CSI-RS), or paging signals.
 8. The method of claim 1, wherein the first BS comprises a first Integrated Access and Backhaul (IAB) node of an IAB network and the second BS comprises a second IAB node of the IAB network, wherein an access node (AN) function of the first IAB node is to perform a RACH procedure with a User Equipment (UE) function of the second IAB node over a wireless backhaul link between the first IAB node and the second IAB node, and wherein performing the RACH procedure includes receiving the RACH preamble.
 9. A method for wireless communication by a first Base Station (BS), comprising: obtaining a Random Access Channel (RACH) configuration to be used for transmitting a RACH signal in a cell served by the first BS or in a neighboring cell; determining at least one symbol after at least one PRACH occasion according to the RACH configuration as invalid for one or more downlink transmissions by the first BS; and transmitting the one or more downlink transmissions based on the determination.
 10. The method of claim 9, wherein determining the at least one symbol as invalid for the one or more downlink transmissions avoids interference to the one or more downlink transmissions from the RACH signal.
 11. The method of claim 9, wherein determining the at least one symbol after the at least one PRACH occasion according to the RACH configuration as invalid comprises determining the RACH signal is to be transmitted by a second BS in the neighboring cell using the at least one PRACH occasion.
 12. The method of claim 11, wherein the second BS is in a vicinity of at least one of the first BS, a User Equipment (UE) served by the first BS, or another BS served by the first BS.
 13. The method of claim 9, wherein determining the at least one symbol after the at least one PRACH occasion according to the RACH configuration as invalid comprises determining the RACH signal is to be transmitted by a User Equipment (UE) served by the first BS using the at least one PRACH occasion.
 14. The method of claim 9, wherein determining the at least one symbol after the at least one PRACH occasion according to the RACH configuration as invalid comprises determining the RACH signal transmitted in the at least one PRACH occasion is to interfere with the one or more downlink transmissions by the first BS in the at least one symbol after the at least one PRACH occasion.
 15. The method of claim 9, wherein the one or more downlink transmissions comprise one or more downlink transmissions on at least one of an access link to at least one User Equipment (UE) or a wireless backhaul link to another BS.
 16. The method of claim 9, wherein determining the at least one symbol comprises determining a default symbol.
 17. The method of claim 9, wherein determining the at least one symbol comprising receiving a configuration from a network configuring the at least one symbol.
 18. The method of claim 17, where receiving the configuration from the network comprises receiving the configuration via at least one of remaining system information (RMSI), other system information (OSI), downlink control information (DCI), radio resource control (RRC) signaling, a medium access control control element (MAC-CE), or a handover message.
 19. A method for wireless communication by a User Equipment (UE) served by a first Base Station (BS), comprising: obtaining a Random Access Channel (RACH) configuration to be used for transmitting a RACH signal in a cell served by the first BS or in a neighboring cell; determining at least one symbol after at least one PRACH occasion according to the RACH configuration as invalid for one or more downlink transmissions to be received from the first BS; and receiving the one or more downlink transmissions from the first BS based on the determination.
 20. The method of claim 19, wherein determining the at least one symbol as invalid for the one or more downlink transmissions avoids interference to the one or more downlink transmissions from the RACH signal. 